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From: Casey Schaufler <casey@schaufler-ca.com>
To: Stephen Smalley <sds@tycho.nsa.gov>, Simon McVittie <smcv@collabora.com>
Cc: casey.schaufler@intel.com, jmorris@namei.org,
	linux-security-module@vger.kernel.org, selinux@vger.kernel.org,
	keescook@chromium.org, john.johansen@canonical.com,
	penguin-kernel@i-love.sakura.ne.jp, paul@paul-moore.com,
	Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [PATCH v14 22/23] LSM: Add /proc attr entry for full LSM context
Date: Mon, 10 Feb 2020 10:32:17 -0800	[thread overview]
Message-ID: <37fa9076-6f15-0261-3bcf-1883236f9c3f@schaufler-ca.com> (raw)
In-Reply-To: <04442c9f-430e-c922-b078-7cff8f36a45f@tycho.nsa.gov>

On 2/10/2020 6:55 AM, Stephen Smalley wrote:
> On 2/10/20 8:25 AM, Stephen Smalley wrote:
>> On 2/10/20 6:56 AM, Simon McVittie wrote:
>>> On Mon, 03 Feb 2020 at 13:54:45 -0500, Stephen Smalley wrote:
>>>> The printable ASCII bit is based on what the dbus maintainer requested in
>>>> previous discussions.
>>>
>>> I thought in previous discussions, we had come to the conclusion that
>>> I can't assume it's 7-bit ASCII. (If I *can* assume that for this new
>>> API, that's even better.)
>>>
>>> To be clear, when I say ASCII I mean a sequence of bytes != '\0' with
>>> their high bit unset (x & 0x7f == x) and the obvious mapping to/from
>>> Unicode (bytes '\1' to '\x7f' represent codepoints U+0001 to U+007F). Is
>>> that the same thing you mean?
>>
>> I mean the subset of 7-bit ASCII that satisfies isprint() using the "C" locale.  That is already true for SELinux with the existing interfaces. I can't necessarily speak for the others.
>
> Looks like Smack labels are similarly restricted, per Documentation/admin-guide/LSM/Smack.rst.  So I guess the only one that is perhaps unclear is AppArmor, since its labels are typically derived from pathnames?  Can an AppArmor label returned via its getprocattr() hook be any legal pathname?

Because attr/context (and later, SO_PEERCONTEXT) are new interfaces
there is no need to exactly duplicate what is in attr/current (later
SO_PEERSEC). I already plan to omit the "mode" component of the
AppArmor data in the AppArmor hook, as was discussed earlier. I would
prefer ASCII, but if AppArmor needs bytestrings, that's what we'll
have to do.

>
>>> I thought the conclusion we had come to in previous conversations was
>>> that the LSM context is what GLib calls a "bytestring", the same as
>>> filenames and environment variables - an opaque sequence of bytes != '\0',
>>> with no further guarantees, and no specified encoding or mapping to/from
>>> Unicode (most likely some superset of ASCII like UTF-8 or Latin-1,
>>> but nobody knows which one, and they coould equally well be some binary
>>> encoding with no Unicode meaning, as long as it avoids '\0').
>>>
>>> If I can safely assume that a new kernel <-> user-space API is constrained
>>> to UTF-8 or a UTF-8 subset like ASCII, then I can provide more friendly
>>> APIs for user-space features built over it. If that isn't possible, the
>>> next best thing is a "bytestring" like filenames, environment variables,
>>> and most kernel <-> user-space strings in general.
>>>
>>>      smcv
>>>
>>
>


  reply	other threads:[~2020-02-10 18:32 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200124002306.3552-1-casey.ref@schaufler-ca.com>
2020-01-24  0:22 ` [PATCH v14 00/23] LSM: Module stacking for AppArmor Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 01/23] LSM: Infrastructure management of the sock security Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 02/23] LSM: Create and manage the lsmblob data structure Casey Schaufler
2020-01-24 14:21     ` Stephen Smalley
2020-01-24  0:22   ` [PATCH v14 03/23] LSM: Use lsmblob in security_audit_rule_match Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 04/23] LSM: Use lsmblob in security_kernel_act_as Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 05/23] net: Prepare UDS for security module stacking Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 06/23] Use lsmblob in security_secctx_to_secid Casey Schaufler
2020-01-24 14:29     ` Stephen Smalley
2020-01-24  0:22   ` [PATCH v14 07/23] LSM: Use lsmblob in security_secid_to_secctx Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 08/23] LSM: Use lsmblob in security_ipc_getsecid Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 09/23] LSM: Use lsmblob in security_task_getsecid Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 10/23] LSM: Use lsmblob in security_inode_getsecid Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 11/23] LSM: Use lsmblob in security_cred_getsecid Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 12/23] IMA: Change internal interfaces to use lsmblobs Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 13/23] LSM: Specify which LSM to display Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 14/23] LSM: Ensure the correct LSM context releaser Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 15/23] LSM: Use lsmcontext in security_secid_to_secctx Casey Schaufler
2020-01-24  0:22   ` [PATCH v14 16/23] LSM: Use lsmcontext in security_inode_getsecctx Casey Schaufler
2020-01-24  0:23   ` [PATCH v14 17/23] LSM: security_secid_to_secctx in netlink netfilter Casey Schaufler
2020-01-24  0:23   ` [PATCH v14 18/23] NET: Store LSM netlabel data in a lsmblob Casey Schaufler
2020-01-24 14:36     ` Stephen Smalley
2020-01-24  0:23   ` [PATCH v14 19/23] LSM: Verify LSM display sanity in binder Casey Schaufler
2020-01-24  0:23   ` [PATCH v14 20/23] Audit: Add subj_LSM fields when necessary Casey Schaufler
2020-01-24  0:23   ` [PATCH v14 21/23] Audit: Include object data for all security modules Casey Schaufler
2020-01-24  0:23   ` [PATCH v14 22/23] LSM: Add /proc attr entry for full LSM context Casey Schaufler
2020-01-24 14:42     ` Stephen Smalley
2020-01-24 16:20       ` Stephen Smalley
2020-01-24 19:28         ` Casey Schaufler
2020-01-24 20:16           ` Stephen Smalley
2020-01-27 20:05             ` Simon McVittie
2020-02-03 20:54               ` John Johansen
2020-01-27 22:49             ` Casey Schaufler
2020-01-31 22:10             ` Casey Schaufler
2020-02-03 18:54               ` Stephen Smalley
2020-02-03 19:37                 ` Stephen Smalley
2020-02-03 21:39                   ` Casey Schaufler
2020-02-04 13:37                     ` Stephen Smalley
2020-02-04 17:14                       ` Casey Schaufler
2020-02-10 11:56                 ` Simon McVittie
2020-02-10 13:25                   ` Stephen Smalley
2020-02-10 14:55                     ` Stephen Smalley
2020-02-10 18:32                       ` Casey Schaufler [this message]
2020-02-10 19:00                         ` John Johansen
2020-02-11 15:59                           ` Stephen Smalley
2020-02-11 17:58                             ` John Johansen
2020-02-11 18:35                               ` Casey Schaufler
2020-02-11 19:11                                 ` John Johansen
2020-02-10 18:56                       ` John Johansen
2020-02-03 21:02             ` John Johansen
2020-02-03 21:43               ` Casey Schaufler
2020-02-03 22:49                 ` John Johansen
2020-02-03 20:59           ` John Johansen
2020-01-24  0:23   ` [PATCH v14 23/23] AppArmor: Remove the exclusive flag Casey Schaufler
2020-01-24 15:05   ` [PATCH v14 00/23] LSM: Module stacking for AppArmor Stephen Smalley
2020-01-24 21:04   ` Stephen Smalley
2020-01-24 21:49     ` Casey Schaufler
2020-01-27 16:14       ` Stephen Smalley
2020-01-27 16:56         ` KASAN slab-out-of-bounds in tun_chr_open/sock_init_data (Was: Re: [PATCH v14 00/23] LSM: Module stacking for AppArmor) Stephen Smalley
2020-01-27 17:34           ` Casey Schaufler
2020-01-27 17:16         ` [PATCH v14 00/23] LSM: Module stacking for AppArmor Casey Schaufler

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